A tortilla is a baked grain product which originated in Mexico and is now widely consumed throughout the world. The word tortilla as used herein refers to such a baked grain product having a variety of shapes, including a circular shape, formed from a relatively flat dough. While the present invention concerns the production of tortillas, the invention also may also successfully used in the production of food products having other shapes.
As the demand for tortillas has grown, the methods and the apparatus for automatically producing tortillas in high volumes has become well known. In the conventional automated system, a dough is produced by cooking whole corn and grinding it wet or by combining instant corn masa flour with water in a commonly available mixer. This dough is generally referred to as "masa". However, the term "masa" as used herein refers to this corn dough and other doughs having similar characteristics. The masa is often fed into an extruder which compresses the masa and outputs it in the form of a generally continuous stream to a pneumatic cutter. The pneumatic cutter chops the masa into generally cylindrical pieces, generally known as "logs". The logs are usually carried on a conveyor to a masa hopper, which gravity feeds the masa to several successive pairs of generally opposed, cylindrical rollers for compression into a sheet having the thickness required for tortilla production. The final pair of opposed rollers are generally known as "sheeter" rollers because they produce a thin sheet of masa. This "sheeted" masa is then cut into the desired tortilla shape by a commonly available rotary cutter, which usually cuts circles of varying diameter. The cut masa is then baked, cooled, and packaged by commonly available commercial food processing equipment.
A portion of an automatic masa processing system is shown in the Driscoll U.S. Pat. No. 2,869,971. The masa processing system described by Driscoll has an endless belt conveyor for feeding masa to a masa hopper. The masa within the masa hopper is then gravity fed into a pair of opposed, counter-rotating primary rollers which compress the masa into a wide curtain of an intermediate thickness. The curtain then moves along a conveyor to a set of sheeter rollers for a final compression into the sheet having a thickness suitable to form the desired tortillas. The sheeted masa is then moved, via conveyor, through a rotating cutter which stamps circular shapes in the masa sheen. Although the rest of the Driscoll apparatus is designed to manufacture food chips from the cut masa, the remainder of the process of baking and cooling tortillas, which only generally concerns this invention, is well known and is schematically shown in the Cope et al. U.S. Pat. No. 4,978,548. Also by way of reference, another Matuszak et al. U.S. Pat. No. 4,640,843, describes a masa extruder and a masa hopper feeding two primary rollers and one associated sheeter roller.
The inventors of the present invention have no reason not to believe that the masa processing system previously described is not generally effective and safe. However, under certain conditions, there may be some drawbacks associated with masa processing systems generally designed according to the prior art. One such drawback can be the danger associated with the pneumatic cutter. The pneumatic cutter has a reciprocating blade which could injure an attending worker if that worker places his or her hands under the operating blade.
Another drawback can be associated with the conveyors intended to transport the masa logs from the pneumatic cutter to the masa hoppers. With increasing demand for tortillas, many companies now desire to operate several parallel production lines, each line having its own masa hopper and its own associated subsequent rolling, cutting, cooking, cooling, and packaging apparatus. Generally, because one masa mixer and extruder can output enough masa to adequately supply several production lines, it is desirable to have an automatic masa hopper feed system capable of maintaining an adequate supply of masa within each masa hopper. However, the conveyors designed according to the prior art simply move masa logs from the pneumatic cutter to one masa hopper. Thus, a masa handling system built according to the prior art could require several conveyors, each running independently from the pneumatic cutter to an associated masa hopper. Furthermore, human attendants could be required to monitor the level of masa in each masa hopper and guide the masa logs onto the conveyors which are running to near-empty masa hoppers. Such a system could have evident disadvantages due to the labor cost of the attendants and the awkwardness of the manual channeling of masa to each conveyor. Furthermore, if the system utilizes only one conveyor running past the masa hoppers in series, the unwanted labor expense is also necessary because human attendants could be required to maintain the masa levels by manually carrying the masa logs from the conveyor to a near-empty masa hopper.
Yet another drawback can be associated with the masa hoppers generally designed according to the prior art. Unwanted gas bubbles can become trapped in the masa and cause voids in the wide masa curtain output by the primary rollers. When this occurs, the voids persist as the masa continues through the sheeter rollers and the rotary cutter, causing imperfectly formed tortillas to be produced. To eliminate the voids, human attendants must manually compress the masa while it is in the masa hopper, resulting in undesirable increased costs.
One final drawback associated with the primary rollers designed according to the prior art can be the tendency of the masa curtain to adhere to the primary rollers after its initial compression. If the masa curtain exits from the primary rollers in a fashion whereby it is stuck to the surface of one of the rollers, the curtain can be carried around the primary roller and away from the sheeter rollers. As a result, the now of masa to the sheeter rollers can be substantially disrupted.
It should, therefore, be appreciated that there still is a need for masa processing system that has the following features: the safe separation of the masa into individual logs; the automatic distribution of those logs to the masa hoppers requiring resupply; the automatic removal of gas bubbles from the masa within the masa hopper; and the prevention of the masa curtain from becoming stuck to the primary rollers. Accordingly, the present invention fulfills all of these needs.